The benefit under 35 Usc xc2xa7119 is claimed of the filing date of: Application No. 10206284.6 in Germany on Feb. 15, 2002. A certified copy of said priority document is attached.
The invention concerns a grinding wheel fixture. The grinding wheel fixture serves for the fixture of dressable grinding wheels, in particular of grinding worms.
In the machining of workpieces on grinding machines, an important pre-requisite for the attainment of high grinding quality is that the grinding spindle runs with as little vibration as possible. Since the grinding spindle is connected to a grinding wheel, in particular a grinding worm, by way of a grinding wheel fixture, this is only attainable if the grinding wheel and the accommodating grinding wheel fixture are together in a high grade state of balance. For this reason the balancing of grinding wheel and grinding wheel fixture takes place in the assembled state on a balancing machine and/or, as long as the grinding machine is provided with a balancing device, in the state of fixture on the grinding spindle. An automatic balancing device suited to this purpose is described in DE 42 22 535. The single-plane balancing device with balancing lugs rotatable by motor is located in the centre of rotation of the grinding wheel. Since, however, for the attainment of a high quality of balance, the balancing range of a balancing device incorporated on the machine is necessarily small as in DE 42 22 535, and balancing on the machine is limited to one balancing plane (static balancing), broad grinding wheels in particular must be previously balanced dynamically by hand, i.e. in two balancing planes, to a high quality of balance on a balancing machine in the state of assembly with the grinding wheel fixture.
DE-A-196""47""452 discloses a grinding wheel fixture with three balancing lugs, which are displaceably located in a common groove, thus permitting a manual balancing in one plane.
Cases moreover occur in which the state of balance of the grinding wheel alters during grinding. This can be caused, for example, by material removal in later dressing operations due to inhomogenity in the grinding wheel, or due to geometrical alterations on the grinding wheel periphery. An example of this is found in grinding worms which are employed for the continuous generating grinding of gears. In such cases, even if a balancing device is provided on the grinding machine, the grinding process must be interrupted from time to time, and the dynamic balancing process repeated on the balancing machine.
In order to allow dynamic balancing, the grinding wheel fixtures are provided with a concentric annular groove on each of their end faces, in which groove balancing lugs can be displaced and fixed in the desired position. By altering the position of the balancing lugs an alteration in the state of balance can be achieved. Shifting of the balancing lugs takes place by hand, whereupon they are clamped in the appropriate angular position according to the measure of out-of-balance indicated by the balancing machine. The balancing lugs are usually of roughly the same size without observation of tolerance specifications.
As especially in the case of large module grinding worms the initial out-of-balance after fitting the grinding worm to the fixture body can be substantial due to the emergence of the grinding worm threads at the end faces, balancing lugs of relatively large mass are required. To enable a high quality of balance to nevertheless be attained with these large masses, the angular positions of the balancing lugs must correspond very exactly with the position indicated on the balancing machine. This is only attainable with difficulty, and demands time consuming, repeated measuring and correcting with every initial and repeat balancing operation.
It is an object of the invention to provide a device which permits the quick, simple, and yet precise balancing of a grinding wheel fixture together with its grinding wheel.
This object is achieved with a grinding wheel fixture having the characteristics of claim 1.
The grinding wheel fixture according to the invention is provided with at least two groups of balancing lugs which are arranged on the same end face of the grinding wheel fixture, the groups being capable of being displaced to and fixed in any desired angular positions independent of each other. To this purpose the individual groups of balancing lugs are arranged in the same balancing plane or in closely adjacent balancing planes.
The balancing process can thus be divided into an initial balancing with a first group of balancing lugs and a fine balancing with a second group of balancing lugs. Initial balancing is preferably performed with heavier balancing lugs than the fine balancing.
In a first embodiment these balancing planes are arranged one beside the other in the axial direction, in that the balancing lugs are located in a counter-recessed annular groove. In another embodiment the annular grooves are arranged radially adjacent, each pair of balancing lugs being located in its own annular groove, and the grooves being concentrically adjacent.
The individual groups of balancing lugs differ in the masses of the individual balancing lugs, which are preferably of a ratio between 1:5 and 1:20.
A circular scale is preferably provided on the end face of the grinding wheel fixture, which permits a fairly accurate positioning of the balancing lugs. By this means, even in the case of high demands on the state of balance, a subsequent correction of the position of the balancing lugs can generally be avoided.
Further advantageous embodiments are indicated in the dependent claims.